Magnetite Nanoparticles-Supported APTES as a Powerful and Recoverable Nanocatalyst for the Preparation of 2-Amino-5,10-dihydro- 5,10-dioxo-4H-benzo[g]chromenes and Tetrahydrobenzo[g]quinoline-5,10- diones

Graphical Abstract:

Abstract:

Aim and Objective: This study introduces a green and effective approach for the preparation
of biologically-active heterocyclic compounds including 2-amino-5,10-dihydro-5,10-dioxo-4Hbenzo[
g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones using one-pot multi-component
reactions in the presence of Fe3O4@SiO2-NH2 nanocomposite. The preparation and use of aminofunctionalized
Fe3O4@SiO2 as a powerful and reusable nanocatalyst is described. The catalyst was
characterized by spectral techniques including FT-IR, SEM, XRD, EDX and VSM analysis. This
method offers the advantages of high yields, short reaction times, comfortable work-up and reusability
of the catalyst.

Material and Method: The amino-functionalization silica-coated magnetite nanocomposite was
prepared by three step method and the structure elucidation of the nanocatalyst has been done using
various spectroscopic analyses. Then, the Fe3O4@SiO2-NH2 nanocomposite was used in the multicomponent
synthesis of 2-amino-5,10-dihydro-5,10-dioxo-4H-benzo[g]chromenes and
tetrahydrobenzo[g]quinoline-5,10-diones under reflux conditions. All of the products were analyzed
with m.p., 1H NMR, 13C NMR and FT-IR spectroscopy techniques. The study on the recoverability of
the nanocatalyst showed the recovered Fe3O4@SiO2-NH2 nanocomposite could be reused sixth
consecutive times with a little-decreased activity.

Results: Amino-functionalized SiO2 coated Fe3O4 nanocomposite exhibited superparamagnetic
behavior and strong magnetization at room temperature. The average crystallite sizes of the catalyst
was about 50-60 nm. The obtained magnetic nanocomposite showed excellent catalytic activity as a
new heterogeneous magnetic catalyst for the synthesis of some benzo[g]chromenes and
tetrahydrobenzo[g]quinoline-5,10-diones. We propose that NH2 groups on the surfaces of
nanocomposite act as the Brønsted base and cause to dehydrogenation of substrates to promote the
reactions.

Conclusion: It was found that Fe3O4@SiO2-NH2 nanocomposite act as an eco-friendly and efficient
catalyst for one-pot synthesis of three/four component condensation reactions. In this research, aminofunctionalized
Fe3O4@SiO2 was used as recoverable catalyst for the synthesis of 2-amino-5,10-
dihydro-5,10-dioxo-4H-benzo[g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones under reflux
conditions. The significant advantages of this method are the reasonably simple work-up, little catalyst
loading, short reaction times, excellent yields, non-hygroscopic quality and reusability of the
nanocatalyst which is in good agreement with green chemistry disciplines.

Combinatorial Chemistry & High Throughput Screening

Title:Magnetite Nanoparticles-Supported APTES as a Powerful and Recoverable Nanocatalyst for the Preparation of 2-Amino-5,10-dihydro- 5,10-dioxo-4H-benzo[g]chromenes and Tetrahydrobenzo[g]quinoline-5,10- diones

Abstract:Aim and Objective: This study introduces a green and effective approach for the preparation
of biologically-active heterocyclic compounds including 2-amino-5,10-dihydro-5,10-dioxo-4Hbenzo[
g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones using one-pot multi-component
reactions in the presence of Fe3O4@SiO2-NH2 nanocomposite. The preparation and use of aminofunctionalized
Fe3O4@SiO2 as a powerful and reusable nanocatalyst is described. The catalyst was
characterized by spectral techniques including FT-IR, SEM, XRD, EDX and VSM analysis. This
method offers the advantages of high yields, short reaction times, comfortable work-up and reusability
of the catalyst.

Material and Method: The amino-functionalization silica-coated magnetite nanocomposite was
prepared by three step method and the structure elucidation of the nanocatalyst has been done using
various spectroscopic analyses. Then, the Fe3O4@SiO2-NH2 nanocomposite was used in the multicomponent
synthesis of 2-amino-5,10-dihydro-5,10-dioxo-4H-benzo[g]chromenes and
tetrahydrobenzo[g]quinoline-5,10-diones under reflux conditions. All of the products were analyzed
with m.p., 1H NMR, 13C NMR and FT-IR spectroscopy techniques. The study on the recoverability of
the nanocatalyst showed the recovered Fe3O4@SiO2-NH2 nanocomposite could be reused sixth
consecutive times with a little-decreased activity.

Results: Amino-functionalized SiO2 coated Fe3O4 nanocomposite exhibited superparamagnetic
behavior and strong magnetization at room temperature. The average crystallite sizes of the catalyst
was about 50-60 nm. The obtained magnetic nanocomposite showed excellent catalytic activity as a
new heterogeneous magnetic catalyst for the synthesis of some benzo[g]chromenes and
tetrahydrobenzo[g]quinoline-5,10-diones. We propose that NH2 groups on the surfaces of
nanocomposite act as the Brønsted base and cause to dehydrogenation of substrates to promote the
reactions.

Conclusion: It was found that Fe3O4@SiO2-NH2 nanocomposite act as an eco-friendly and efficient
catalyst for one-pot synthesis of three/four component condensation reactions. In this research, aminofunctionalized
Fe3O4@SiO2 was used as recoverable catalyst for the synthesis of 2-amino-5,10-
dihydro-5,10-dioxo-4H-benzo[g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones under reflux
conditions. The significant advantages of this method are the reasonably simple work-up, little catalyst
loading, short reaction times, excellent yields, non-hygroscopic quality and reusability of the
nanocatalyst which is in good agreement with green chemistry disciplines.